Blowtorch



W. M. HOUGHTON BLOWTORGH Filed Dec. 5, 1923 m M6 5 WW NW N 5 M m W 1 5 v @Q iii Patented Nov. 25, 1924..

()FFICE.

BLOWTORGH.

Application filed December.

To all whom it may concern;

Be it known that I, WILLIAM M. HOUGH- TON, a citizen of the United States of America, and resident of Chestnut Hill, in the county of Middlesex and State of Massachusetts, have invented new and useful Improvements in Blowtorches, of which the following is a specification.

My invent-ion relates to apparatus for handling fluids, and particularly to blow torches in which the flow of compressed air or other gas is to be controlled.

Blow torches and other types of burners employing compressed air or other gas to stimulate combustion, to direct the pat-h of the burning fluid, or to accomplish other objects, are generally supplied with the compressed gas, say air, at high pressure in order to minimize the space required for storage and handling of the air and in order to allow of a wide range of adjustment of the pressure of the air as it is used. Heretofore, it has been customary to adjust the pressure of the air by throttling the stream of air being used. However, adjustment by throttling is not only very wasteful of the energy released by the expansion of the air from its initial high pressure to the pressure at which it is used, but produces unreliable and irregular results. When the initial pressure of the compressed air is large and the pressure of the delivered air is small, as is the case in most blow torches, serious difliculty arises in controlling the air pressure, owing to the large changes in pressure resulting from slight changes in the setting of the throttling valve, and owing to fluctuations in the volume and pressure of the air delivered, even when the adjustment of the throttling valve remains fixed, these fluctuations being apparently due in part at least to an unstable turbulent flow of the air provoked by the throttling valve. Objects of my invention are to overcome the above defects, to provide a blow torch or other burner employing compressed air or other oxidizing gas in which provision is made for conveniently and positively adjusting the operation of the burner, to minimize the weight of the burner, to minimize irregularities in the flow of the gas, to utilize the energy released by expansion of the compressed gas for increasing the volume of gas flow, to operate the burner with less expenditure of the initially compressed gas than in prior burners doing the same Serial No. 678,602.

amount of work, and generally to improve the construction, adjustment and economy of operation of apparatus of the kind re ferred to.

These objects are attained by an embodiment of the invention illustrated in the accompanying drawing, in which Fig. 1 is a side view partly in section of a blow torch; and

Fig. 2 is an enlarged longitudinal section of a portion of Fig. 1.

In Fig. 1, the blow torch 10, having the burner portion 11 and the handle portion 12, is supplied with fuel gas through the hose 13 and with compressed oxidizing gas, hereinafter referred to as air, through the hose 14 which is connected with a tank or other source of compressed air, not shown.

Fuel conduit 15 discharges fuel through its open end 15 in burner 11, the volume I of flow being controlled by valve 16 of well known construction. The compressed air conduit comprising a high pressure section 17 and a low pressure section 18 discharges air through its open end 18 adja cent the open end 15 of conduit 15. The low pressure section 18 is of smaller diameter than fuel conduit 15 being positioned coaxially within conduit 15 in burner 11, thus affording an annular passage for fuel gas between the conduits. Conduit 18 passes through the wall of conduit 15 and extends fro-m burner 11 to an open end flaring to form a funnel shaped receiver 19 which constitutes a part of the aspirator or pump 20. The nozzle 21 of the aspirator is positioned axially of the receiver 19 and connected to high pressure conduit 17 to discharge a jet of air at high velocity into funnel 19, the volume of air projected from the nozzle being adjusted by turning the screw threaded needle valve 22 to advance or retract the conical end 23 of the needle within the circular orifice 24 thereby to vary the annular opening between the needle and nozzle.

The inner walls 25 of nozzle 21 diverge conically from the orifice 24 with a greater angle than that of the conical needle, thus providing a restricted passage having its smallest cross section at the orifice 24. This arrangement permits of reducing the effective size of orifice 24 and the flow of compressed air therethrough to any desired degree by the needle valve, at the same time reducing the tendency toward unstable turbulent flow of the air and maintaining at a minimum the losses due to throttling of the high pressure air. The shape of the outer walls 26 of the nozzle and the shape of receiver 19 still further reduce the tendency for turbulent flow to take place, the contour of these parts being so designed as to conform closely with the general stream lines in the flowing air, so that frictional and other losses tending to reduce the pressure of the air or the efliciency of the pump are maintained at a minimum.

In operating the torch, a stream of rapidly moving air projected through orifice 24 and into receiver 19 entrains air from the atmosphere into the receiver, thus utilizing the energy released by expansion of the compressed air from the high pressure conduit to augment the flow of compressed air in the low pressure conduit. It has been found that very fine and easily controllable adjustments of the air flow can be made in a torch designed as described. Air pressures of from to 150 pounds per square inch, or higher, in conduit 17 may be efliciently utilized by the aspirator.

It is to be noted that in prior burners and blow torches employing compressed air to be fed directly into the flame, substantially the entire amount of air projected into the flame is derived from the compressed air tank or other supply, whereby the supply is rapidly depleted; whereas in the case of applicants torch a relatively small amount of compressed air delivered through nozzle 21 suffices to impel a large volume of air through conduit 18, thus aifording considerable saving in the expense of compressed air consumed, and in the bulk of apparatus required to handle the compressed air.

Inasmuch as the aspirator can have relatively small weight and bulk and still perform its functions satisfactorily, the total weight and bulk of the blow torch may actually be reduced below that in which the usual form of valve, such as valve 16, is employed to throttle the air, this feature being important to enable easy manipulation of the blow torch over long periods of time.

I claim:

1. A blow torch comprising a burner, means for conveying a compressed oxidizer to said burner, means independent of said first means for conveying fuel to .said burner, said first means comprising spaced conduits and a nozzle between said conduits for directing a fluid stream from one into the other conduit in the direction of said burner whereby air adjacent thereto is entrained and transmitted to said burner.

2. A blow torch comprising a burner, a fuel duct leading to the burner, means for conveying a compressed oxidizer to the burner, said means comprising spaced conduits, an end portion of one conduit terminating at a point in advance of said fuel duct, a nozzle connected to the other conduit for directing a fluid stream into the first conduit in the direction of the burner whereby air adjacent thereto is entrained and transmitted to said burner, and means for regulating the flow of fluid through said nozzle.

3. A blow torch comprising a burner, a conduit in said burner having one end terminating at a point in rear of the outer end of the burner and the other end terminating outside the burner, a flaring end portion on said outer end, a nozzle for directing a compressed oxidizer into said flaring end portion thereby to entrain air into said conduit, and a fuel duct leading to said burner at a point remote from the outer end thereof.

Signed by me at Boston, Massachusetts.

this th day of November, 1923.

HOUGI-ITQN. 

